System of preoperative planning and provision of patient-specific surgical aids

ABSTRACT

A method of preoperative planning comprises creating a virtual model of a native patient tissue; placing a virtual device into a desired device orientation relative to the virtual model of the native patient tissue; specifying at least one structural change to the native patient tissue to facilitate placement of the virtual device in the desired device orientation; creating a virtual model of an altered patient tissue responsive to the specifying at least one structural change to the native patient tissue; and fabricating a tangible representation of a bone using the virtual model of the altered patient tissue.

RELATED APPLICATION

The present application is a continuation of U.S. Non-Provisionalapplication Ser. No. 13/282,550 filed on Oct. 27, 2011 which claimspriority on U.S. Provisional Application Ser. No. 61/408,392, filed onOct. 29, 2010, and incorporated herewith by reference.

TECHNICAL FIELD

The present invention relates to a preoperative planning system and,more particularly, to a system of preoperative planning and provision ofpatient-specific surgical aids.

BACKGROUND OF THE INVENTION

The scapula, commonly known as the “shoulder blade”, is a flat,triangular bone that lies over the back of the upper ribs. A rightscapula 100 is depicted in posterior, anterior, and right side views inFIGS. 1A, 1B, and 1C, respectively. The posterior surface of the scapula100 can be readily felt through a patient's skin. The scapula 100 servesas an attachment point for some of the muscles and tendons of the arm,neck, chest, and back, and aids in the movements of the arm andshoulder. The scapula 100 is also well padded with muscle, so that itmay be difficult to palpate boney landmarks. The rear surface of eachscapula 100 is divided into unequal portions by a spine 102. This spine102 leads to a head 104, which ends in the acromion process 106. Acoracoid process 108 forms a prominence of the shoulder that curvesforward and down below the clavicle (collarbone, not shown). Theacromion process 106 joins the clavicle and provides attachments formuscles of the arm and chest muscles. The acromion process 106 is a bonyprominence at the top of the scapula 100. On the head 104 of the scapula100, between the acromion and coracoid processes 106 and 108, is adepression or cavity called the glenoid vault 110, shown partially indashed line in the Figures. The glenoid vault 110 joins with the head ofthe upper arm bone (humerus, not shown) in a ball-and-socket manner toenable articulation of the shoulder joint thereby formed. Similarly,though not shown, an acetabulum of the hip joint mates with a head of anupper leg bone (femur) to form an analogous ball-and-socket manner forhip joint articulation.

For treatment of various problems with the shoulder, hip, or other bodyjoint or bone (such as degenerative arthritis and/or traumatic injury),one method of providing relief to a patient is to replace thearticulating surfaces with an artificial or prosthetic joint. In thecase of a shoulder, the humerus and glenoid vault 110 articulatingsurfaces are replaced. In the case of a hip, the femur and acetabulumarticulating surfaces can be replaced. Both of these examples are ofball-and-socket type joints. Hinge-type joints, such as the knee orelbow, and static/fixed skeletal components, such as the long bones ofthe arm or leg, as well as interfaces such as those between spinalvertebrae and intervertebral discs, could also be subject to replacementand/or repair by the implantation of artificial or prosthetic componentsor other fixation devices related to the treatment of fractures, thesequelae of trauma, congenital pathology, or other issues causing a lackof ideal function. For clarity of description, the subject applicationwill be hereafter described as the rehabilitation and/or replacement ofa patient's shoulder joint.

In such surgical procedures, pain relief, increased motion, and/oranatomic reconstruction of the joint are goals of the orthopedicsurgeon. With multiple variations in human anatomy, prosthetic systemsmust be carefully designed, chosen, and implanted to accuratelyreplicate the joints that they replace or the bone structures that theyaim to change (in any manner).

A shoulder replacement procedure may involve a partial shoulderreplacement (not shown) or the total shoulder replacement shown in FIG.2. In a total shoulder replacement procedure, a humeral component 212having a head portion is utilized to replace the natural head portion ofthe upper arm bone, or humerus 214. The humeral component 212 typicallyhas an elongated stem which is utilized to secure the humeral componentto the patient's humerus 214, as depicted. In such a total shoulderreplacement procedure, the natural bearing surface of the glenoid vault110 is resurfaced, lined, or otherwise supplemented with a cup-shapedglenoid component 216 that provides a bearing surface for the headportion of the humeral component 212. The depicted total shoulderreplacement of FIG. 2 is an “anatomical” shoulder replacement. A“reverse” shoulder replacement is also known in the art.

Standard prosthetic glenoid components 216 are available in a number ofdifferent sizes and configurations. However, most are designed for usein an scapula having minimal bone loss or deformity. When the scapulahas bone loss and/or significant pathology due to disease or trauma, thestandard glenoid component 216 may be difficult to implant and/or maynot enable desired shoulder function, if it cannot be implanted in apreferred manner. The surgeon may thus need to substantially modify thepatient's glenoid vault 110 during surgery in an attempt to make thestandard glenoid component 216 fit into the glenoid vault. Pre-surgicalplanning tools are available to help the surgeon anticipate the changeswhich will be needed to reform the patient's pathological anatomy.However, the surgeon cannot always readily determine whether even aremodeled glenoid vault 110 will fit as desired with a standardprosthesis because the surgeon does not know how a “normal” glenoidvault 110 (for which the standard prosthesis is designed) should beshaped for that patient.

It is known to use computer aided design (“CAD”) software to designcustom prostheses based upon imported data obtained from a computerizedtomography (“CT”) scan of a patient's body. For example, mirror-imagedCT data of a patient's contralateral “normal” joint could be used, ifthe contralateral joint does not also display a pathological anatomy.However, using a unique prosthesis design for each patient can result infuture biomechanical problems resulting from a non-proven design andtakes away the familiarity that the surgeon will likely have withstandardized prosthesis designs. Thus, prosthesis designs that areentirely customized are considered sub-optimal solutions.

Further, detailed preoperative planning, using two- or three-dimensionalimages of the shoulder joint, often assists the surgeon in compensatingfor the patient's anatomical limitations. During the surgery, forexample, an elongated pin may be inserted into the surface of thepatient's bone, at a predetermined trajectory and location, to act as apassive landmark or active guiding structure in carrying out thepreoperatively planned implantation. This “guide pin” may remain as aportion of the implanted prosthetic joint or may be removed before thesurgery is concluded. This type of pin-guided installation is common inany joint replacement procedure—indeed, in any type of surgicalprocedure in which a surgeon-placed fixed landmark is desirable.

In addition, and again in any type of surgical procedure, modernminimally invasive surgical techniques may dictate that only a smallportion of the bone or other tissue surface being operated upon isvisible to the surgeon. Depending upon the patient's particular anatomy,the surgeon may not be able to precisely determine the location of theexposed area relative to the remaining, obscured portions of the bonethrough mere visual observation. For example, in a shoulder surgery, thescapula 100 is mobile along the chest wall and it therefore may bedifficult to define the fixed relationship of the glenoid vault 110 tothe body of the scapula 100 (i.e., using the plane of the scapula as areference to the glenoid vault) and/or the body of the scapula to anexternal coordinate system in the operating room. These factors,particularly in a minimally invasive surgical procedure, may make itdifficult for the surgeon to orient the glenoid vault during surgery.Again, a guide pin may be temporarily or permanently placed into theexposed bone surface to help orient the surgeon and thereby enhance theaccuracy and efficiency of the surgical procedure.

One goal of shoulder surgery may be to modify the pathologic bone tocorrect pathologic version to be within the normal range or the normalversion of the patient's native anatomy before the bone loss occurred.During surgery, and particularly minimally invasive procedures, theplane of the scapula may be difficult or impossible to determine bydirect visual inspection, resulting in the need for assistive devices ormethods to define both the pathologic version present at the time ofsurgery and the intended correction angle.

It is generally believed that there is a preferred orientation for theglenoid component 216 to provide a full range of motion and to minimizethe risk of dislocation. Some example orientations of the glenoidcomponent 216 relative to the glenoid face are about 5.degree. ofanteversion to about 15.degree. of retroversion; average version isabout 1-2.degree. of retroversion. This broadly replicates the naturalangle of the glenoid. However, the specific angular orientation of theglenoid portion varies from patient to patient.

With a view to overcoming these and other disadvantages, somearrangements have been recently suggested in which a three-dimensionalintraoperative surgical navigation system is used to render a model ofthe patient's bone structure. This model is displayed on a computerscreen and the user is provided with intraoperative three-dimensionalinformation as to the desired positioning of the instruments and theglenoid component 216 of the prosthetic implant. However, surgicalnavigation arrangements of this type are not wholly satisfactory sincethey generally use only a low number of measured landmark points toregister the patient's anatomy and to specify the angle of theprosthetic implant component (e.g., a glenoid component 216), which maynot provide the desired level of accuracy. Further, the informationprovided by such systems may be difficult to interpret and may evenprovide the user with a false sense of security. Moreover, these systemsare generally expensive to install and operate and also have high usertraining costs.

Various proposals for trial prosthetic joint components have been madein an attempt to overcome the problems associated with accuratelylocating the glenoid component 216 of the prosthetic implant. Whilethese trial systems may help with checking whether the selected positionis correct, they are not well-suited to specify the correct positioninitially, and thus there still is user desire for a system which mayassist a user in placement of prosthetic implant component in a preparednative tissue site.

Finally, due to factors such as the high cost of operating room time andthe patient detriment sometimes posed by lengthy surgeries, the surgeonor other user may wish to simulate a surgical procedure duringpreoperative planning, in order to become familiar with the tasks thatwill be required and possibly reduce the time and/or actions needed toperform the surgery.

In summary, preoperative planning and/or simulation, regardless of theplanning tasks undertaken or the nature of the changes to be made to thepatient's native tissue, will generally reduce the need forintraoperative imaging in most surgical procedures and should result indecreased operative time and increased positional accuracy, all of whichare desirable in striving toward a positive patient outcome.

SUMMARY OF THE INVENTION

In an embodiment of the present invention, a method of preoperativeplanning, the method comprises: creating a virtual model of a nativepatient tissue; placing a virtual device into a desired deviceorientation relative to the virtual model of the native patient tissue;specifying at least one structural change to the native patient tissueto facilitate placement of the virtual device in the desired deviceorientation; creating a virtual model of an altered patient tissueresponsive to the specifying at least one structural change to thenative patient tissue; and fabricating a tangible representation of abone using the virtual model of the altered patient tissue.

In an embodiment of the present invention, a method of preoperativeplanning and provision of patient-specific surgical aids is described. Adevice for placement in engagement with a native patient tissue ischosen. A predetermined device orientation for the device with respectto the native patient tissue is virtually specified. At least onelandmark is virtually placed in a predetermined landmark orientationwith respect to the predetermined device orientation. A patient-specificplacement guide is virtually modeled, the patient-specific placementguide being simultaneously mated with the device and registered with atleast one landmark when the device is in the predetermined deviceorientation. A patient-specific template is virtually modeled, thepatient-specific template being configured to mate with the nativepatient tissue, the patient-specific template having a landmark guidingfeature configured to place the landmark in the predetermined landmarkorientation when the patient-specific template is mated with the nativepatient tissue. A physical version of the patient-specific placementguide is created. A physical version of the patient-specific template iscreated.

In an embodiment of the present invention, a computer readable medium isdescribed. The computer readable medium has computer executableinstructions for receiving scanned image data based on an imaging scanof a native patient tissue. An image of the native patient tissue basedon the received scanned image data is displayed. Placement of an imageof a selected device is displayed over the image of the native patienttissue. The image of the selected device over the image of the nativepatient tissue is reoriented into a predetermined device orientation.Placement of an image of at least one selected landmark is displayed ina predetermined landmark orientation over the image of the nativepatient tissue. Placement of an image of a selected guide blank isdisplayed in a predetermined guide orientation over the image of thenative patient tissue and the image of the selected device, when theimage of the selected device is in the predetermined device orientation.The selected guide blank is provided with at least one orientingfeature, the provided orienting feature being registered with at leastone selected landmark when the image of a selected guide blank is in thepredetermined guide orientation and the image of the selected device isin the predetermined device orientation. A physical guide is fabricatedfrom the selected guide blank having the provided orienting feature.

In an embodiment of the present invention, a method of preoperativeplanning and provision of at least one patient-specific surgical aid isdescribed. A virtual model of a native patient tissue is created. Aphysical model of the native patient tissue as a tangible representationof the virtual model of the native patient tissue is created. Thephysical model of the native patient tissue includes at least oneinformation feature providing clinically useful information to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be made tothe accompanying drawings, in which:

FIG. 1A is an anterior view of a right scapula;

FIG. 1B is a posterior view of the scapula of FIG. 1A;

FIG. 1C is a side view of the scapula of FIG. 1A;

FIG. 2 is a partial sectional anterior view of a prosthetic shoulderjoint in a patient;

FIG. 3 is a flowchart describing one embodiment of the presentinvention;

FIGS. 4-10 are example user views of a program for generating theembodiment of FIG. 3;

FIGS. 11A-11B are schematic views depicting a use environment for theembodiment of FIG. 3;

FIGS. 12A-12C are schematic views depicting placement options for oneelement of the embodiment of FIG. 3 in a first configuration;

FIGS. 13A-13C are schematic views depicting placement options for oneelement of the embodiment of FIG. 3 in a second configuration;

FIGS. 14A-14B are schematic views depicting options for one element ofthe embodiment of FIG. 3 in the first configuration; and

FIG. 15 is a schematic view of a computer system that can be employed toimplement systems and methods described herein, such as based oncomputer executable instructions running on the computer system.

DESCRIPTION OF EMBODIMENTS

The patient tissue is shown and described herein at least as a scapula100 and the prosthetic implant component is shown and described hereinat least as a glenoid component 216, but the patient tissue andcorresponding prosthetic implant component could be any desired typessuch as, but not limited to, hip joints, shoulder joints, knee joints,ankle joints, phalangeal joints, metatarsal joints, spinal structures,long bones (e.g., fracture sites), or any other suitable patient tissueuse environment for the present invention. For example, the prostheticimplant component could be an internal fixation device (e.g., a boneplate), a structure of a replacement/prosthetic joint, or any othersuitable artificial device to replace or augment a missing or impairedpart of the body.

The term “lateral” is used herein to refer to a direction indicated bydirectional arrow 118 in FIG. 10; the lateral direction in FIG. 10 liessubstantially within the plane of the drawing and includes all of thesuperior, inferior, anterior, and posterior directions. The term“longitudinal” is used herein to refer to a direction definedperpendicular to the plane created by directional arrow 118, with thelongitudinal direction being substantially into and out of the plane ofthe drawing in FIG. 10 and representing the proximal (toward the medialline of the body) and distal (out from the body) directions,respectively.

In accordance with the present invention, FIG. 3 is a flowchartdepicting one example series of steps of a method of preoperativeplanning and provision of patient-specific surgical aids. In firstaction block 320, a virtual three-dimensional model of a native patienttissue is created. A “native” patient tissue herein is used to referencethe status of the actual, physical patient tissue at the time that thesurgery is being planned. For example, the native patient tissue mayhave been in the “native” state from birth, or may instead be subject toa congenital or acquired deficiency and accordingly be in an alteredstate as compared to the patient tissue originally present in thepatient. Regardless of the mechanism by which the patient tissue cameinto the “native” condition, the “native” patient tissue is used hereinto reference the expected state of the patient tissue at the time of theoperation—when the user cuts into the patient's body, the native patienttissue is what will be found at the surgical site.

The virtual model of the native patient tissue may be based upon, forexample, scanned image data taken from an imaging scan of the nativepatient tissue. The term “model” is used herein to indicate a replica orcopy of a physical item, at any relative scale and represented in anymedium, physical or virtual. The patient tissue model may be a total orpartial model of a subject patient tissue, and may be created in anysuitable manner. For example, and as presumed in the below description,the patient tissue model may be based upon computer tomography (“CT”)data imported into a computer aided drafting (“CAD”) system.Additionally or alternatively, the native patient tissue model may bebased upon digital or analog radiography, magnetic resonance imaging, orany other suitable imaging means. The patient tissue model willgenerally be displayed for the user to review and manipulatepreoperatively, such as through the use of a computer or other graphicalworkstation interface. While this description presumes athree-dimensional model, one of ordinary skill in the art could use atwo-dimensional model in a similar manner to that shown and describedherein, without harm to the present invention. An example of a virtualmodel of the native patient tissue is the native patient tissue model422 shown in FIGS. 4-10.

FIGS. 4-10 pictorially depict the preoperative planning proceduredescribed in the FIG. 3 flowchart. FIGS. 4-10 are example user views ofa computer program and/or system for implementing a method of using thepresent invention, with a perspective view on the left side of eachFigure and coronal, sagittal (looking distally from underneath theperspective view, as shown), and transverse views, respectively, fromtop to bottom on the right side of each Figure.

During preoperative planning with a system such as that described, theuser can view the native patient tissue model 422 and, based uponknowledge of other patient characteristics (such as, but not limited to,height, weight, age, and activity level), choose a desired device,described hereafter as a stock device 424, for use in the surgicalprocedure. This use may include placement in engagement with a nativepatient tissue model 422, as shown in second action block 326 of FIG. 3.Visually, such as in the user view of FIG. 4, an image of the selecteddesired stock device 424 may be placed over the native patient tissuemodel image.

A desired device could be the depicted stock prosthetic implant, acustom prosthetic implant, a stock or custom instrument (not shown), orany other desired item. Because three-dimensional image models areavailable of many instruments and prosthetic implants, whether stock orcustom, the user may be able to “install” the instrument or prostheticimplant virtually in the native patient tissue model 422 via thepreoperative computer simulation described herein. During such asimulation, the user can automatically and/or manually adjust orreorient the position of the virtual stock device 424 with respect tothe virtual native patient tissue model 422, even to the extent ofsimulating the dynamic interaction between the two, as may be helpful torefine the selection, placement, and orientation of the stock device fora desired patient outcome. The stock device 422 may be chosen from alibrary of available stock devices, with the choice based upon anyfactor or characteristic desired.

The term “stock” is used herein to indicate that the component indicatedis not custom-manufactured or -configured for the patient, but isinstead provided as a standard inventory item by a manufacturer. Aparticular stock component may be selected automatically by the systemand/or manually by the user from a product line range (e.g., theaforementioned library) of available components, optionally with theuser specifying a desired configuration, general or particular size(e.g., small, medium, large, or a specific measurement), material, orany other characteristic of the component. Indeed, the stock componentcould be manufactured only after the user has selected the desiredoptions from the range of choices available. However, the stockcomponent is differentiated from a custom-manufactured or bespokecomponent in that the stock component is agnostic and indifferentregarding a particular patient anatomy during the design andmanufacturing processes for an instrument, prosthetic implant, or othercomponent intended for that patient, while the patient anatomy is aninput into at least one design and/or manufacturing process for acustom-manufactured component. The following description presumes theuse of a stock prosthetic implant and stock instrument, though one ofordinary skill in the art will be able to provide for the use of thepresent invention with a custom-manufactured prosthetic implant orinstrument, instead.

At third action block 328 of FIG. 3, the stock device 424 is placed, orreoriented, into a predetermined device orientation relative to thenative patient tissue model 422, to achieve the position shown in FIG.4. An orientation of a structure, as used herein, includes both theabsolute location of the structure upon or with respect to anotherstructure and the arrangement or positioning in space of the structure(e.g., rotation, pitch, yaw, camber, or any other placement-relatedvariable of the structure).

The system may place the stock device 424 into the predetermined deviceorientation automatically by the system and/or manually by the user,based upon any suitable criteria. For example, the system may provide atleast two optional device orientations and compare the optional deviceorientations to each other based upon any desired device property(ies),in a weighted or unweighted manner. Device properties that could factorinto the comparison include at least one of device size, device shape,device material, number of fasteners to be used, type of fasteners, sizeof fasteners, shape of fasteners, amount of patient tissue alteration,type of patient tissue alteration, orientation of the stock devicerelative to an other stock device (e.g., orientation of one part of aprosthetic joint relative to another part of the prosthetic joint whichhas already been [virtually] placed with respect to the native patienttissue model), and physical quality of the native patient tissue. Aplurality of optional device orientations could be compared to oneanother based on these or any other suitable factors, in any suitablemanner (e.g., using a decision algorithm or comparison scheme). It iscontemplated that certain device properties may be more important thanothers, and that the comparisons will be made automatically by thesystem and/or manually by the user to allow for compromises—if needed—oncertain device properties in order to strive for a better overalloutcome.

Once the comparison(s) is (are) made, the user and/or system chooses anoptional device orientation based upon the comparison and designates thechosen optional device orientation as the predetermined deviceorientation. The predetermined device orientation of the stock device424 with respect to the native patient tissue model 422 is shown in theFIG. 4 view. As is especially apparent in the coronal (top right) andtransverse (bottom right) portions of FIG. 4, there may be some overlapor superposition between the stock device 424 and the native patienttissue model 422. This superposition is permissible in the virtualenvironment of the described system and may helps to indicate areas ofthe native patient tissue model 422 which could be targeted foralteration during placement of the stock device 424.

Once a chosen stock device 424 has been virtually placed in a desiredorientation with respect to the native patient tissue model 422 (it willbe understood that some mechanical modification might need to be made tothe actual native patient tissue to accomplish this implant placement insitu), the placement of any fasteners or other penetrating structures430 (e.g., a drill, guide pin, or other surgical tool), when present,may also be planned through the use of the computer simulation.Consideration of the location, amount, and pathology of the patienttissue, any of the above device properties, or any other desiredfactors, may be taken into account in this optional penetratingstructure 430 planning. The penetrating structure(s) 430 may be chosenfrom a library of available penetrating structures.

Manually and/or with automatic computer assistance, the user canexperiment with various fastener sizes, placements, and orientations forsecuring the stock prosthetic implant to the patient tissue, and/or withvarious other types of penetrating structure 430 insertions into thenative patient tissue model 422 similarly to the previously describeddevice placement, until reaching at least one predetermined penetrationorientation (such as that shown in FIG. 4) for at least one penetratingstructure(s) 430 to be used with the surgical procedure being planned,as described in fourth action block 332 of the FIG. 3 flowchart. Whenthe penetrating structure 430 positioning has been finalized, with thestock device 424 virtually positioned in a predetermined deviceorientation with respect to the patient tissue, a location and targettrajectory 434 may be defined for each of the penetrating structures 430present (if any) to follow during installation. The term “trajectory” isused herein to indicate an invisible line along which an elongate bodywill travel to reach the predetermined penetration orientation.

Once the predetermined device orientation and any desired predeterminedpenetration orientation(s), when present, are known, the displayedimages of the selected stock device 424 and/or of any includedpenetrating structures 430 may be removed from the displayed image ofthe native patient tissue model 422, for greater clarity in followingportion(s) of the preoperative planning system. The displayed images ofthe selected stock device 424 and/or of any included penetratingstructures 430 may be reinstated and re-removed, as desired, during anyphase of the below operations.

As shown in fifth action block 336 of FIG. 3, at least one landmark 538(shown in FIG. 5) may be placed in at least one predetermined landmarkorientation relative to the native patient tissue model 422. Thelandmark(s) 538, when present, represent a chosen point in space and/orindicate a chosen direction/orientation relative to the native patienttissue model 422 and are used to convey positional information to theuser during a surgical procedure. For example, a guide pin is displayedas a three-dimensional landmark 538 a spaced apart from the stock device424 over the image of the native patient tissue model 422 in FIG. 5,while an aperture or cavity formed in the native patient tissue model isshown as a two-dimensional landmark 538 b (i.e., represented by a crossmark when seen from above or below) corresponding to a central portionof the stock device in FIG. 5. In fact, the “negative” aperture-typelandmark 538 b of FIG. 5 is configured to receive a device shaft 540 ofthe stock device 424, which helps to locate and stabilize the stockdevice with respect to the native patient tissue model 422. One ofordinary skill in the art would readily be able to instead provide a“positive” pin- or shaft-type landmark (not shown) protruding from thenative patient tissue model 422 and adapted to be received in a cavity(not shown) of another type of device, in an axle-type manner.

Regardless of the number, location, type, or any other characteristicsof the provided landmark(s) 538, it is contemplated that the user willwant to transfer the landmarked information to the actual patient tissueduring the surgical procedure. To that end, a patient-specific templatemay be created using the system described herein. The landmark 538 couldalso or instead be placed during the surgical procedure using a roboticsurgical aid, adjustable reusable (e.g., “dial-in”) tools,intraoperative imaging, or any other suitable placement aid.

As shown at sixth action block 342 of FIG. 3, a patient-specifictemplate is generated, which may be accomplished by the system withsteps represented in user views such as the sequence of FIGS. 6-7. Asshown in FIG. 6, a template blank 644 is placed into a desired (final)predetermined template orientation with respect to the native patienttissue model 422. The template blank 644 may be selected, automaticallyand/or manually, from a library of available template blanks and may beplaced, again automatically and/or manually, into the predeterminedtemplate orientation based upon any of the above device properties orany other desired factors.

As is particularly apparent in the coronal (top right) and transverse(bottom right) portions of FIG. 6, at least a portion of the nativepatient tissue model 422 and at least a portion of the template blank644 (virtually) overlap to create a superposed volume 646 of space whichis occupied by both the native patient tissue model and the templateblank. Since this superposed volume 646 is impracticable during theactual physical surgical procedure, the superposed volume 646 is (again,virtually) removed from the template blank 644 to create a matingsurface 748 of the template blank adjacent the native patient tissuemodel 422. In other words, the system adjusts the dimensions of thebottom template surface 748 to mate with a surface of the native patienttissue model 422. The term “mate” is used herein to indicate arelationship in which the contours of two structures are at leastpartially matched or coordinated in at least two dimensions.

The mating surface 748 may be seen in particularly the coronal (topright) and transverse (bottom right) portions of FIG. 7. Thepatient-specific template 750 may be, for example, the type disclosed inco-pending U.S. patent application No. to be determined, filed Oct. 27,2011, titled “System and Method for Association of a Guiding Aid with aPatient Tissue” and claiming priority to U.S. Provisional PatentApplication No. 61/408,359, filed Oct. 29, 2010 and titled “System andMethod for Association of a Guiding Aid with a Patient Tissue”, theentire contents of both of which are incorporated herein by reference.

Regardless of its nature, the patient-specific template 750 virtuallycontains or embodies at least one predetermined landmark orientation andhas at least one landmark guiding feature 752 configured to place alandmark 538 in the predetermined landmark orientation when thepatient-specific template 750 is mated with the native tissue model 422.As shown in FIG. 7, at least one landmark guiding feature 752 is anaperture through the patient-specific template 750 which is configuredto guide a penetrating structure, such as a guide pin or drill bit, intothe native patient tissue model 422 at a predetermined penetrationlocation and with a specified target trajectory 434.

When the landmark 538 is a two-dimensional landmark such as a marking onthe surface of the native patient tissue, the target trajectory 434 ofthe landmark guiding feature 752 will likely be of little to no import.In contrast, when the landmark 538 is a three-dimensional landmark suchas a drilled hole or an elongate guide pin, the target trajectory 434 ofthe landmark may bear some significance. In FIG. 7, the depicted targettrajectory 434 corresponds to a desired drilling trajectory for anaperture which receives a device shaft 540 at a later stage of thesurgical procedure. In this sense, therefore, at least one of thelandmark guiding features 752 shown in FIG. 7 may also serve as apenetration-guiding feature.

Once the landmark(s) 538 have been virtually placed into thepredetermined landmark orientation(s) at fifth action block 336 of FIG.3 and the patient-specific template 750 created at sixth action block342, the stock device 424 may be (virtually) re-placed upon the nativepatient tissue model 422 and at least one patient-specific placementguide 958 may be generated at seventh action block 356 of FIG. 3. Thepatient-specific placement guide 958 may be configured to interactsimultaneously with at least one previously placed landmark (here, atleast guide pin-type landmark 538 a) and with the stock device 424 whenthe stock device is in the predetermined device orientation.

The patient-specific placement guide 958 may be, for example, similar toany of those disclosed in co-pending U.S. patent application No. to bedetermined, filed Oct. 27, 2011, titled “System and Method for Assistingwith Attachment of a Stock Implant to a Patient Tissue” and claimingpriority to U.S. Provisional Patent Application No. 61/408,324, filedOct. 29, 2010 and titled “System and Method for Assisting withAttachment of a Stock Implant to a Patient Tissue”, the entire contentsof both of which are incorporated herein by reference, or in co-pendingU.S. patent application No. to be determined, filed Oct. 27, 2011,titled “System and Method for Assisting with Attachment of a StockInstrument to a Patient Tissue” and claiming priority to U.S.Provisional Patent Application No. 61/408,376, filed Oct. 29, 2010 andtitled “System and Method for Assisting with Attachment of a StockInstrument to a Patient Tissue”, the entire contents of both of whichare incorporated herein by reference.

Regardless of the type of patient-specific placement guide 958 provided,the patient-specific placement guide may be generated similarly to thepatient-specific template 750. Namely, a placement guide blank 854,shown in FIG. 8, may be automatically or manually selected, optionallyfrom a library of available placement guide blanks. It is contemplatedthat the placement guide blank 356 may be selected responsive to theselection of the stock device 424, because in many applications of thepresent invention, the patient-specific placement guide 958 will nestinto or mate with some physical feature of the stock device. Forexample, and as shown in particularly the transverse view of FIG. 8, theplacement guide blank 356 may nest with a portion of the stock device424 substantially collinear with the device shaft 540 to help positivelylocate the patient-specific placement guide with respect to the stockdevice.

The placement guide blank 854, once selected by any suitable procedure,may then be (virtually) altered to register with at least one landmark538, as shown in FIG. 9 when the patient-specific placement guide 958 ismated with the stock device 424 and the stock device is in thepredetermined device orientation. Registration of the patient-specificplacement guide 958 with a chosen landmark 538 helps to indicate thatthe stock device 424 has achieved the predetermined device orientationwhen the patient-specific placement guide 958 is mated or nested withthe stock device and the stock device is in contact with the nativepatient tissue model. The term “register” or “registration” is usedherein to indicate a predetermined condition of correct alignment orproper relative position between a landmark 538 (of any type) and somefeature of the structure (here, the patient-specific placement guide958) being registered. For example, when the landmark 538 is atwo-dimensional marking on the native patient tissue model 422, theregistration might occur when an inscribed mark on the patient-specificplacement guide 958 aligns with the two-dimensional landmark.

As another example, and as shown in FIG. 9, the landmark 538 a might bea three-dimensional landmark such as a guide pin. In this instance, thepatient-specific placement guide 958 includes at least one orientingfeature 960 (having previously been provided to the guide blank) whichwill register with the selected landmark 538 a by contact with the guidepin embodying that landmark when the patient-specific placement guide958 is mated or nested with the stock device 424 (as shown in FIG. 9)and the stock device is in contact with the native patient tissue modelin the predetermined device orientation. In the view of FIG. 9, thestock device 424 is not yet in the predetermined device orientation asindicated by the separation of the orienting feature 960 and thelandmark 538 a, though the patient-specific placement guide 958 is matedwith the stock device, as can be seen in particularly the coronal andtransverse views of FIG. 9.

In addition to the guiding/orienting function provided by thepatient-specific placement guide 958, at least one penetration-guidingfeature 962 (four shown in FIG. 9) may be provided by thepatient-specific placement guide. Here, the target trajectory 434 aindicates a target trajectory and associated penetration locationassociated with a landmark 538 b, whereas the target trajectories marked434 b (shown in dashed line in the coronal and transverse views sincenot strictly present in those sections) and the associated penetrationlocations in FIG. 9 are associated with one or more penetratingstructures (not shown in FIG. 9), such as fasteners, drill bits, othersurgical tools, or any other components used in the surgical procedurewhich the user wishes to guide with the assistance of thepatient-specific placement guide 958.

FIG. 10 is similar to FIG. 9, though the stock device 424 has beenreoriented into the predetermined device orientation, as indicated bythe registration of the orienting feature 960 and the landmark 538 a. Ascan also been seen in FIG. 10, the body of the patient-specificplacement guide 958 has been rotated sufficiently to bring thepenetration-guiding features 962 into a different rotational orientationwith respect to the native patient tissue model 422 than that of FIG. 9.The target trajectories 434 b of the penetration-guiding features 962should be in the desired penetration locations with respect to thenative patient tissue model 422 when the stock device 424 has beenbrought into the predetermined device orientation.

Once the patient-specific template 750 and/or the patient-specificplacement guide 958 have been generated as desired, including anydesired features as described above, a physical version of thepatient-specific template is created at eighth action block 364 of FIG.3 and a physical version of the patient-specific placement guide iscreated at ninth action block 366 of FIG. 3. These physical versions ofthe patient-specific template 750 and/or the patient-specific placementguide 958 are tangible (e.g., material and palpable) representations ofthe virtual versions of the corresponding items as manipulated,adjusted, and otherwise created using a system similar to that shown viathe user views of FIGS. 4-10.

Optionally, and as shown in tenth action block 368 of FIG. 3, a physicalthree-dimensional version of the native patient tissue model 422 may befabricated as a tangible (e.g., material and palpable) representation ofthe virtual version of the native patient tissue model. This physicalnative patient tissue model (not shown) may be useful in preoperativeplanning, visualization, and consideration of the surgical procedure bythe user (e.g., for assisting with performing the surgery using patientspecific templates and/or adjustable surgical instruments). To that end,the physical native patient tissue model may include at least oneinformation feature providing clinically useful information to the user.“Clinically useful” information is used herein to indicate anyinformation, other than the structure of the native patient tissueitself, that assists one of ordinary skill in the art with some pre-and/or intra-operative task. An “information feature” is any physicalfeature or characteristic of the physical native patient tissue modelwhich signifies or communicates the clinically useful information to theuser, optionally in combination with a preoperative plan. For example,only a portion of the scapula 100 may be fabricated as a physical nativepatient tissue model, with planar faces bounding the omitted portions ofthe scapula. Those planar faces may be chosen at predetermined distancesfrom, and/or with predetermined orientations with respect to, astructure of interest on the physical native tissue model. As anotherexample, an information feature may be a physical characteristic thatfacilitates transfer of information from the native patient tissue model422 to the actual patient anatomy, perhaps by facilitating the settingof an adjustable, reusable tool such as that disclosed in co-pendingU.S. patent application Ser. No. 12/854,362, filed Aug. 11, 2010 andtitled “Method and Apparatus for Insertion of an Elongate Pin into aSurface”, the entire contents of which are incorporated herein byreference.

In one example embodiment of a physical native tissue model givingspatial information, for instance, a planar face bounding a lowerportion of the physical native tissue model may be substantiallyparallel to a transverse plane of the scapula 100. Often the patient isoriented during surgery such that the plane of the scapula 100 is notidentifiable with reference to the orientation of the glenoid vault 110in the surgical field. Accordingly, by placing the physical nativetissue model with an information feature in a known position (e.g, byplacing a lower face of the physical native tissue model flat on atable), one of ordinary skill in the art can readily envision obscuredportions of the patient's native tissue anatomy through reference to thephysical native tissue model, which may be configured to provide theuser with a visualization of the native patient tissue in the sameorientation as in the patient's body but without the surrounding tissuethat prevents the user from directly seeing structures such as, but notlimited to, the acromion process 106, the coracoid process 108, or anyother structure of the scapula 100. This may be particularly useful whenthe physical native tissue model is fabricated at a 1:1 scale with thenative patient anatomy, but also will have utility when the model isscaled up or down from the patient's actual tissue.

As another example embodiment of a physical native tissue model givingspatial information, a pin-receiving aperture may be provided in thephysical native tissue model, to receive a guide pin and thusdemonstrate a certain direction or axis to the user with respect to thenative tissue. As a corollary to this example, an axis-, direction-, orplane-indicating structure may extend from the physical native tissuemodel to serve as a user visualization aid or reference.

The physical native tissue model could be used to interact with animplant or instrument before or during the surgical procedure, as well.For example, a user could rehearse certain interactions of an implant orinstrument with the physical native tissue model to gain familiaritywith the way that the implant or instrument is likely tointraoperatively interact with the patient's native tissue.

Physical native tissue models with information features or specificlandmarks related to the preoperatively developed surgical plan are notcurrently provided or used as references during surgical procedures. Theavailability of a physical native tissue model to use as a reference inthis manner may supplement or even supplant the need for intraoperativeimaging, which is likely to reduce cost, operating room clutter, andtime required for the surgical procedure.

The patient's name, identification number, surgeon's name, and/or anyother desired identifier may be molded into, printed on, attached to, orotherwise associated with the physical version(s) of thepatient-specific template 750, the patient-specific placement guide 958,and/or the native patient tissue model 422 in a legible manner. Thetangible representations of the patient-specific template 750, thepatient-specific placement guide 958, and/or the native patient tissuemodel 422 may be made by any suitable method such as, but not limitedto, selective laser sintering (“SLS”), fused deposition modeling(“FDM”), stereolithography (“SLA”), laminated object manufacturing(“LOM”), electron beam melting (“EBM”), 3-dimensional printing (“3DP”),contour milling from a suitable material, computer numeric control(“CNC”), other rapid prototyping methods, or any other desiredmanufacturing process.

Once the physical versions of the patient-specific template 750, thepatient-specific placement guide 958, and/or the native patient tissuemodel 422 have been manufactured and prepared for use (e.g.,mechanically or chemically cleaned, cured, sterilized, or the like)using any suitable process(es), they are available for use duringsurgical procedures as described above and in the incorporatedreferences.

The preoperative planning system disclosed herein allows the user toexperiment with different placements and selections of stock devices 424and/or custom or patient-specific components in an effort to producepositive patient outcomes. FIGS. 11A-14B depict various examples ofsteps, alternate options, and considerations that one of ordinary skillin the art may find useful in preoperative planning, particularly withrespect to selection of the stock device 424 and of the predetermineddevice orientation.

FIGS. 11A-11B depict a transverse view of a native patient tissue model422 of a typical clinical case of a patient with osteoarthritis, havingmoderate bone loss. The scapular plane 1170 is perpendicular toreference plane 1172. The reference plane also represents the 0.degree.reference from which glenoid version is measured. The lower portion ofFIGS. 11A-11B is posterior and the top portion of these Figures isanterior, as shown by direction arrow 118′. The diagonal dashed linelabeled 1174 represents the native glenoid plane of the patient. In thiscase, the native glenoid plane 1174 exhibits a retroversion angle ofapproximately 26.degree. from the reference plane 1172. Glenoid versionin the normal population is reported to commonly be between 5.degree. ofanteversion and 15.degree. of retroversion. The average normal glenoidversion is approximately 1-2.degree. of retroversion.

The goal of arthroplasty surgery is to correct pathologic anatomy andrestore as best as possible normal anatomy and function. Correctiveoptions range between placing an implant component at the standard idealof perpendicular to the plane of the scapula (0.degree.) up to thepathologic version (in this case, 26.degree. of retroversion). Commonpractice today is to correct version with an attempt to place a stockdevice 424 approximately perpendicular to the scapular plane 1170 (i.e.,lying along the reference plane 1172 at about 0.degree. of version). Forclarity of description, the “angle” of the stock device 424 isreferenced hereafter as being the angle measured from a top face of thestock device, the top face being foremost in the perspective view ofFIG. 4.

There normally will be a secondary surgical goals to minimize removal ofpatient tissue needed to accommodate the stock device 424, seat theentire stock device on the prepared patient tissue surface, and minimizeunwanted perforation of the outer walls of the glenoid vault 110 orother patient tissue by the device shaft 540 or another penetratingstructure 430 used in the surgical procedure or remaining in the patienttissue postoperatively. When formulating a preoperative plan, typicalitems of concern include the bone (or other patient tissue) loss in thepatient, the position and orientation of the normal joint line, andwhere the stock device 424 or other component should be placed to aimtoward a positive patient outcome.

The present inventors have found that an average patient tissue model1176 (e.g., a “vault model”) may be useful in tailoring a surgicalprocedure to fit the needs of an individual patient. A suitable averagepatient tissue model 1176 is described in co-pending U.S. patentapplication Ser. No. 12/043,634, filed Mar. 6, 2008, and titled “Methodand Apparatus for Preparing for a Surgical Procedure”, the contents ofwhich are hereby incorporated by reference in their entirety. In asimilar manner, the shape of an average acetabular vault may be used asa suitable average patient tissue model and have some clinical relevancewhen defining the normal anatomic relationships from the pathologicanatomy in a hip use environment. The average patient tissue model 1176of a glenoid vault 110 is shown superimposed on the native patienttissue model 422 in FIG. 11B. Although this is an “average” view, thecontours of the average patient tissue model 1176 can be seen tosubstantially mirror the contours of the native glenoid vault 110 ofeven the depicted pathologic scapula 100.

FIG. 11B is similar to FIG. 11A, with the addition of an average patienttissue model 1176. The average patient tissue model 1176 helps to definethe location of the normal joint line and the version of the normalglenoid fossa 1178 in a patient-specific manner. The average patienttissue model 1176 may help define reconstruction goals in pathologiccases, and may assist with selection of position and type of a stockdevice 424 or a custom device (not shown). Selection of version for thestock device 424 may be at least partially dependent upon the version ofthe average patient tissue model 1176 which defines patient-specificnormal anatomy. In the patient of FIGS. 11A-14B, normal patient version,based upon the average patient tissue model 1176, may be seen to beapproximately 12.degree. of retroversion, as shown by the angle of therightmost face (in the orientation of the Figures) of the averagepatient tissue model 1176 with respect to reference plane 1172.

When planning a surgical procedure using preoperative imaging, the usermay specify at least one structural change to the native patient tissueto facilitate placement of a stock device in a predetermined deviceorientation. For example, native patient tissue could be drilled,planed, reamed or otherwise removed, or the native patient tissue couldbe built up using bone grafts or other substances, with the latter beingmuch more difficult to do than the former during a standard surgicalprocedure. Using the system described above, a (virtual) altered patienttissue model (not shown) can be generated and viewed or otherwise usedin the preoperative planning. Optionally, a physical three-dimensionalversion of the altered patient tissue model may be fabricated as atangible representation of the virtual version of the altered patienttissue model. When provided, the physical altered patient tissue modelmay also include at least one information feature providing clinicallyuseful information to the user. For example, a landmark 538 (e.g., acavity or aperture) may be present in the physical altered patienttissue model and may therefore be made palpable to the user during thesurgical procedure. The physical altered patient tissue model, whenpresent, may be used and referenced similarly to the aforementionedphysical native patient tissue model.

FIGS. 12A-14B are partial transverse cross-sectional schematic views ofa scapula which depict a comparison of the likely surgical outcomes forvarious preoperative planning options. FIGS. 12A-14B depict various waysin which the native patient tissue model 422 can be compared to areference patient tissue model (regardless of whether any alterationsare made to the native patient tissue model), and the effect of thatcomparison on the predetermined device orientation. The predetermineddevice orientation can be adjusted, automatically by the system and/ormanually by the user, responsive to the comparison of the native patienttissue model 422 to the reference patient tissue model. The referencepatient tissue may be at least one of a (mirrored) image of acontralateral patient tissue of the same or a different patient, a valuetaken from a standard reference patient tissue, a value range taken froma standard reference patient tissue, and the aforementioned averagepatient tissue model 1176. In FIGS. 12A-14B, the reference patienttissue is shown and described as being the average patient tissue model1176. In FIG. 12A, a stock device 424 has been superimposed upon thenative patient tissue model 422 of FIGS. 11A-11B in a version of0.degree. from the coronal plane (shown in FIGS. 11A-13C as scapularplane 1170), with the bottom portion (in the orientation of FIGS.11A-13C) of the stock device being located on an outer surface of thenative patient tissue. Since FIGS. 12A-13C show the scapula 100 havingportions of the native tissue removed to accommodate each stock device424, the patient tissue shown can be described as an altered patienttissue model 1280. The excision of fairly large amounts of nativepatient tissue is likely to adversely affect the dynamics within theshoulder joint. Additionally, the glenoid vault 110 may be shaved downenough that the device shaft 540 is in danger of breaching the glenoidvault wall, which is generally undesirable and can cause patientdiscomfort and possibly result in undesirable reoperation. Accordingly,one goal of a pre-surgical planning process using the average patienttissue model 1176 is to attempt to replicate the total volume (or area,as depicted in the cross-sectional views of FIGS. 12A-14B) of theaverage patient tissue model 1176 with a combination of the total volume(or area) of the altered patient tissue model 1280 and the stock device424.

It is apparent from FIG. 12A that a substantial amount of the nativepatient tissue will have to be removed from the native patient tissuemodel 422 to allow the stock device 424 to seat firmly and maintain the0.degree. version with the stock device 424 substantially centered,posteriorly to anteriorly, upon the glenoid fossa 1178. The device shaft540 in FIG. 12A is in danger of breaching the glenoid vault 110 wall,which should be avoided.

FIG. 12B also shows an altered patient tissue model 1280 with arelatively large volume of native patient tissue removed, though lessremoved than in FIG. 12A. In FIG. 12B, the version is still corrected to0.degree. from the reference plane 1172, but the stock device 424 hasbeen moved upward (in the orientation of the Figures) to distance thedevice shaft 540 from the glenoid vault 110 wall. This shifting of thestock device 424 can be seen to have a different adverse effect,however—namely, the stock device now substantially overhangs theanterior edge of the glenoid fossa 1178.

This problematic 0.degree. version correction is an example of a valuetaken from a standard reference patient tissue—many users will routinelycorrect version in all such cases to 0.degree. as shown. As an exampleof a value range taken from a standard reference patient tissue, theversion may be corrected to a value taken from the range of −5.degree.to +5.degree., with the user's experience and intuition leading to theselection of one value from that range. Another example, in a hipstandard reference patient tissue, might prescribe a range of10-30.degree. of anteversion and 30-55.degree. of abduction for anacetabular prosthetic implantation. However, a seemingly reasonablevalue based upon a standard reference patient tissue—whether for ashoulder, hip, or any other type of surgery—may markedly depart from avalue which leads to an acceptable result for a particular patient.

As a result, users will sometimes employ a mirror image of acontralateral native patient tissue (from that patient or anotherpatient) to use as a reference patient tissue. However, even if there isa contralateral native patient tissue to consult (e.g., the patient isnot an amputee in that respect), the contralateral native patient tissuemay be pathologically or congenitally asymmetrical from even theoriginal state of the native patient tissue which is being surgicallycorrected. Thus, there is a need for another reference patient tissuefor comparison to the native patient tissue model 422.

In the aforementioned co-pending “Method and Apparatus for Preparing fora Surgical Procedure” U.S. patent application, the average patienttissue model 1176 (i.e., the “vault model”) is proposed as providing anappropriate reference patient tissue for a wide range of patients. Theaverage patient tissue model 1176 is shown in FIGS. 12A-13C superimposedover the altered patient tissue model 1280. Accordingly, one of ordinaryskill in the art, with reference to the average patient tissue model1176, will be motivated to preserve more of the native patient tissue byaltering the native tissue model 422, and placing the stock device 424with reference to the average patient tissue model 1176.

In the situation of FIG. 12C, the average patient tissue model 1176helps define the native patient joint line and the native version forthat particular patient. Accordingly, the average patient tissue model1176 helps direct the selection of the stock device 424 to restore thenative joint line and the patient's native version, thereby reducing therisk of excessive bone removal or perforation of the native patienttissue during or after the stock device is installed. FIG. 12C depictsan altered patient tissue model 1280 with the average patient tissuemodel 1176 superposed thereupon and the stock device 424 placedaccording to the average patient tissue model (here, rotated clockwise,in the orientation of the Figures). It can be seen that placement of thestock device 424 in a patient-specific version (informed by the averagepatient tissue model 1176) will center the device shaft 420 (posteriorlyto anteriorly) in the glenoid vault 110, provide more thorough patienttissue contact for the stock device, and result in less patient tissueremoval and greater centering of the stock device on the glenoid fossa1178 as compared to the 0.degree. versions of FIGS. 12A and 12B.Accordingly, the stock device 424 placement in FIG. 12C would seem toprovide a preferred predetermined device orientation compared to theorientations shown in FIGS. 12A and 12B.

FIGS. 13A-13C depict a similar orientation comparison sequence to thatof FIGS. 12A-12C, but including a different stock device 424 a than thatshown in FIGS. 12A-12C. The stock device 424 a includes a thickenedleftmost section (in the orientation of the Figures) which helps tocompensate for the pathologic state of the native patient tissue. Thisselection of this stock device 424 a, having a second configuration ascompared to the first configuration of the stock device 424 of FIGS.12A-12C allows for the combination of the native glenoid vault 110 plusthe stock device 424 a to have a similar, and similarly arranged, volumeof material as that of the average patient tissue model 1176. Thearrangements of FIGS. 13A-13C are analogous to those of FIGS. 12A-12C,excepting the differences in the stock devices 424 and 424 a, andtherefore the description of FIGS. 12A-12C will not be repeated withrespect to 13A-130.

The views of the combination of the altered glenoid vault 110 plus thestock device 424 a of FIGS. 13A-13C may be favorably contrasted with theanalogous views of FIGS. 12A-12C, wherein the combination of the alteredglenoid vault 110 plus the stock device 424 has a substantially smallervolume in the latter when compared to the average patient tissue model1176, and thus the latter will have less strength and ability tomechanically perform for the patient as needed for a suitably long timeafter the surgical procedure. Accordingly, the stock device 424 aselection and placement of FIG. 13C appears to meet the goal ofpreserving native tissue the best of all of the options shown in FIGS.12A-13C.

FIGS. 14A-14B show the effects of device orientation upon the nativepatient tissue model 422. In FIG. 14A, the version has been corrected to0.degree. That is, the target trajectory 534 of the patient-specifictemplate 750 is substantially parallel to the scapular plane 1170. As isapparent in FIG. 14A, the device shaft 540 is cutting markedly into thecoronal bone of the scapula 100 in an undesirable manner, and arelatively large volume of native patient tissue will need to be removed(near the top of FIG. 14A) to accept the stock device 424. In FIG. 14B,the version has been corrected to a value chosen by the user withconsideration of the native patient tissue model 422—the version in FIG.14B is approximately 12.degree. As can be seen, by simply tilting thestock device 424 in FIG. 14B as suggested by the average patient tissuemodel 1176 or by a chosen value out of a value range taken from astandard reference patient tissue, the stock device 424 is seated moresecurely in the glenoid vault 110, with less removal of native patienttissue required.

FIG. 15 illustrates a computer system 1582 that can be employed toimplement systems and methods described herein, such as based oncomputer executable instructions running on the computer system. Theuser may be permitted to preoperatively simulate the planned surgicalprocedure using the computer system 1582 as desired. The computer system1582 can be implemented on one or more general purpose networkedcomputer systems, embedded computer systems, routers, switches, serverdevices, client devices, various intermediate devices/nodes and/or standalone computer systems. Additionally, the computer system 1582 can beimplemented as part of the computer-aided engineering (CAE) tool runningcomputer executable instructions to perform a method as describedherein.

The computer system 1582 includes a processor 1584 and a system memory1586. Dual microprocessors and other multi-processor architectures canalso be utilized as the processor 1584. The processor 1584 and systemmemory 1586 can be coupled by any of several types of bus structures,including a memory bus or memory controller, a peripheral bus, and alocal bus using any of a variety of bus architectures. The system memory1586 includes read only memory (ROM) 1588 and random access memory (RAM)1590. A basic input/output system (BIOS) can reside in the ROM 1588,generally containing the basic routines that help to transferinformation between elements within the computer system 1582, such as areset or power-up.

The computer system 1582 can include one or more types of long-term datastorage 1592, including a hard disk drive, a magnetic disk drive, (e.g.,to read from or write to a removable disk), and an optical disk drive,(e.g., for reading a CD-ROM or DVD disk or to read from or write toother optical media). The long-term data storage 1592 can be connectedto the processor 1584 by a drive interface 1594. The long-term datastorage 1592 components provide nonvolatile storage of data, datastructures, and computer-executable instructions for the computer system1582. A number of program modules may also be stored in one or more ofthe drives as well as in the RAM 1590, including an operating system,one or more application programs, other program modules, and programdata.

A user may enter commands and information into the computer system 1582through one or more input devices 1596, such as a keyboard or a pointingdevice (e.g., a mouse). These and other input devices are oftenconnected to the processor 1584 through a device interface 1598. Forexample, the input devices can be connected to the system bus by one ormore a parallel port, a serial port or a universal serial bus (USB). Oneor more output device(s) 15100, such as a visual display device orprinter, can also be connected to the processor 1584 via the deviceinterface 1598.

The computer system 1582 may operate in a networked environment usinglogical connections (e.g., a local area network (LAN) or wide areanetwork (WAN) to one or more remote computers 15102. A given remotecomputer 15102 may be a workstation, a computer system, a router, a peerdevice or other common network node, and typically includes many or allof the elements described relative to the computer system 1582. Thecomputer system 1582 can communicate with the remote computers 15102 viaa network interface 15104, such as a wired or wireless network interfacecard or modem. In a networked environment, application programs andprogram data depicted relative to the computer system 1582, or portionsthereof, may be stored in memory associated with the remote computers15102.

It is contemplated that multiple versions of the patient-specifictemplate 750 and/or the patient-specific placement guide 958 could becreated during preoperative planning and fabricated as options for theuser to select from during the surgical procedure. For example, the usermay not be able to clear away surrounding (e.g., soft) tissue from thenative patient tissue as well as expected. In this situation, it may beuseful to have a patient-specific template 750 with a smaller footprintfor easier insertion into the surgical wound and manipulation at thesurgical site, even though the smaller footprint means that there isless mating surface 748 to mate with the native patient tissue andprovide positive location assistance for the patient-specific template750.

While aspects of the present invention have been particularly shown anddescribed with reference to the preferred embodiment above, it will beunderstood by those of ordinary skill in the art that various additionalembodiments may be contemplated without departing from the spirit andscope of the present invention. For example, the specific methodsdescribed above for using the described system are merely illustrative;one of ordinary skill in the art could readily determine any number oftools, sequences of steps, or other means/options for virtually oractually placing the above-described apparatus, or components thereof,into positions substantially similar to those shown and describedherein. Any of the described structures and components could beintegrally formed as a single piece or made up of separatesub-components, with either of these formations involving any suitablestock or bespoke components and/or any suitable material or combinationsof materials; however, the chosen material(s) should be biocompatiblefor most applications of the present invention. The mating relationshipsformed between the described structures need not keep the entirety ofeach of the “mating” surfaces in direct contact with each other butcould include spacers or holdaways for partial direct contact, a lineror other intermediate member for indirect contact, or could even beapproximated with intervening space remaining therebetween and nocontact. Though certain components described herein are shown as havingspecific geometric shapes, all structures of the present invention mayhave any suitable shapes, sizes, configurations, relative relationships,cross-sectional areas, or any other physical characteristics asdesirable for a particular application of the present invention. Anadhesive (such as, but not limited to, bone cement) could be used inconjunction with the system and method described herein. Thepatient-specific template 750 and/or the patient-specific placementguide 958 may include a plurality of structures cooperatively formingthe base body and temporarily or permanently attached together in such amanner as to permit relative motion (e.g., pivoting, sliding, or anyother motion) therebetween. The patient-specific placement guide 958 maynot actually be patient-specific but could instead be a stock item insituations where the landmark(s) 538 are placed to “standardize” aparticular native patient tissue model with a standard frame ofreference. Any structures or features described with reference to oneembodiment or configuration of the present invention could be provided,singly or in combination with other structures or features, to any otherembodiment or configuration, as it would be impractical to describe eachof the embodiments and configurations discussed herein as having all ofthe options discussed with respect to all of the other embodiments andconfigurations. Any of the components described herein could have asurface treatment (e.g., texturization, notching, etc.), materialchoice, and/or other characteristic chosen to provide the component witha desired interaction property (e.g., tissue ingrowth, eluting of atherapeutic material, etc.) with the surrounding tissue. The system isdescribed herein as being used to plan and/or simulate a surgicalprocedure of implanting one or more prosthetic structures into apatient's body, but also or instead could be used to plan and/orsimulate any surgical procedure, regardless of whether a non-nativecomponent is left in the patient's body after the procedure. A device ormethod incorporating any of these features should be understood to fallunder the scope of the present invention as determined based upon theclaims below and any equivalents thereof.

Other aspects, objects, and advantages of the present invention can beobtained from a study of the drawings, the disclosure, and the appendedclaims.

The invention claimed is:
 1. A method of preoperative planning, themethod comprising: creating a virtual model of a native patient tissue;placing a virtual device into a desired device orientation relative tothe virtual model of the native patient tissue; specifying at last onestructural change to the virtual model of the native patient tissue tofacilitate placement of the virtual device in the desired deviceorientation, the at last one structural change based on removing tissuefrom the virtual model of the native patient tissue or adding tissue tothe virtual model of the native patient tissue; creating a virtual modelof at least one patient-specific template, the at least onepatient-specific template configured to mate with the virtual model ofthe native patient tissue, the at last one patient-specific templateincluding a landmark guiding feature configured to direct at last onevirtual non-tissue landmark at a predetermined orientation when thepatient-specific template is mated with the virtual model of the nativepatient tissue; creating a virtual model of an altered patient tissueresponsive to specifying the at least one structural change to thenative patient tissue; and fabricating a tangible representation of abone using the virtual model of the altered patient tissue.
 2. Themethod according to claim 1, wherein fabricating the tangiblerepresentation of the bone includes fabricating the tangiblerepresentation using one of selective laser sintering, fused depositionmodeling, stereolithography, laminated object manufacturing, electronbeam melting, 3-dimensional printing, contour milling, computer numericcontrol fabricating.
 3. The method according to claim 1, furthercomprising providing the tangible representation of the bone with atangible version of the virtual device.
 4. The method according to claim3, wherein providing the tangible version of the virtual devicecomprises providing an implant.
 5. The method according to claim 1,wherein specifying the at least one structural change to the nativepatient tissue includes comparing the native patient tissue with areference patient tissue model, the reference patient tissue model beingat least one of a contralateral patient tissue model, a standardreference patient tissue value, a standard reference patient tissuevalue range, and a predetermined average patient tissue model.
 6. Themethod of claim 1, wherein fabricating the tangible representation ofthe bone comprises including at least one information feature providingclinically useful information for a user.
 7. The method of claim 1,wherein placing the virtual device into the desired device orientationcomprises choosing at least one device property, the at least one deviceproperty including at least one of device size, device shape, devicematerial, number of fasteners, type of fasteners, size of fasteners,shape of fasteners, amount of patient tissue alteration, type of patienttissue alteration, and physical quality of the native patient tissue. 8.The method of claim 1, further comprising choosing the virtual devicefrom a library of available virtual devices.
 9. The method of claim 1,further comprising: virtually placing at least one non-tissue landmarkin a predetermined landmark orientation with respect to the desireddevice orientation; virtually modeling at least one patient-specifictemplate, the at least one patient-specific template being configured tomate with the native patient tissue and with the virtual device, thepatient-specific template having a landmark guiding feature configuredto place the non-tissue landmark in the predetermined landmarkorientation when the patient-specific template is mated with the nativepatient tissue and with the virtual device; and creating a tangibleversion of the at least one patient-specific template.
 10. The methodaccording to claim 1, wherein the native patient tissue comprises thebone.
 11. The method according to claim 1, wherein the virtual device isan implant.
 12. The method according to claim 1, wherein the tangiblerepresentation of the bone comprises a representation of patient tissueconfigured to receive the virtual device.
 13. The method according toclaim 12, wherein the virtual device comprises an implant.
 14. Themethod according to claim 1, wherein the tangible representation of thebone differs from the bone in that the tangible representation of thebone is free of a portion corresponding to tissue to be removed from thebone to accommodate the virtual device.
 15. The method according toclaim 1, wherein the tangible representation of the bone differs fromthe bone in that the tangible representation of the bone includes aportion corresponding to tissue to be added from the bone to accommodatethe virtual device.
 16. The method according to claim 1, wherein thetangible representation of the bone comprises a surface of a boneconfigured to receive the virtual device.
 17. The method of claim 1,wherein specifying at least one structural change to the virtual modelof the native patient tissue is based on the placement of the virtualdevice into the desired device orientation relative to the virtual modelof the native patient tissue.
 18. A method comprising: creating avirtual model of a native patient tissue; placing a virtual device intoa desired device orientation relative to the virtual model of the nativepatient tissue; specifying at least one structural change to the virtualmodel of the native patient tissue to facilitate placement of thevirtual device in the desired device orientation, the at last onestructural change based on removing tissue from the virtual model of thenative patient tissue; creating a virtual model of at last onepatient-specific template, the at last one patient-specific templateconfigured to mate with the virtual model of the native patient tissue,the at least one patient-specific template including a landmark guidingfeature configured to direct at least one virtual non-tissue landmark ata predetermined orientation when the patient-specific template is matedwith the virtual model of the native patient tissue; creating a virtualmodel of an altered patient tissue responsive to specifying the at lastone structural change to the native patient tissue; and fabricating atangible representation of a bone using the virtual model of the alteredpatient tissue.
 19. The method of claim 18, further comprising: placingat least one virtual non-tissue landmark in a predetermined landmarkorientation with respect to the desired device orientation; and wherein:the at least one patient-specific template is configured to guide apenetrating structure toward the virtual model of the native patienttissue; and the virtual model of the altered patient tissue is based onthe virtual model of the at least one patient-specific template.